The present invention relates to an improvement in the invention described in my U.S. Pat. No. 3,903,696 entitled "Hydraulic Energy Storage Transmission," issued Sept. 9, 1975. The disclosure of such patent is incorporated herein in its entirety by this reference.
A major problem which is presented with systems which store braking energy and convert it to drive power by hydraulic principles is that such systems require a hydraulic transmission comprising one or more hydraulic motors to be driven by the output from the brake energy accumulator and an engine-driven pump. For vehicular use such hydraulic transmission must of necessity be multi-speed and multi-torque in character, i.e., it must have a selectively variable ratio of output shaft speed and torque with respect to the speed and torque of the engine.
Such multi-speed and torque capability is conventionally accomplished with hydraulic transmissions by the utilization of variable displacement pumps and/or motors in the transmissions. A problem however arises from the fact that such variable displacement pump and motor equipment is customarily of very low efficiency due to the swash plate, wobble plate or other type of mechanical volumetric variation apparatus utilized within the equipment.